I would think a spell to detect the Gift would fall under Intelligo Vim. What would the base effect of such a spell be?
I don't have an answer, but a new question: magig Sensivity may detect the gift? ( I have read of Ladislaus, page 102 of Guardian of the forest)
After a quick read through, I wouldn't think so. It seems Magic Sensitivity can be used only for Auras, Spells (and Items), and Magical Creatures.
Agreed. Sensitivity can only be used on auras, items, and creatures.
I have my core book, but not the supplements. I think True Lineages may detail an apprentice detecting spell. I think.
It's an InVi 20 spell, IIRC.
In which book?
Base 20?
Do Blatant & gentle gift have an effect on it?
What about 'Pre-awakening' detection & while still in the woumb of their mother detections.
Hmmm.. so many questions.
W
It's an old 3rd ed. Grimoire spell. Not canonical anymore, I'm affraid.
A magus îs a creature, so I woulod allow magic sensitivity to affect it. Right, he does not have MR, but the weird area that even regular mundanes notice (the -3 to social rolls) must mark the magus as a light beacon for the senstivity guiy. Even more than MR, since MR or spells do NOT cause a social penalty.
If there is the gentle gift in the equation, I would still allow a roll for magic senstivity. A high roll, but allow it. Maybe +12 or +15. After all you are sensible to the supernatural energies of magic, and this guy has them, even if they are disguissed.
Regards,
Xavi
PS: In fact, I think I already allowed it a few years ago. I can'tr remember the magus developing a specific spell to track a potential apprentice, and he had sensitivity, so there you go. It did not cause a major story hole or anything, I tell you 
Not that gifted children have been so common as to be a dayly usage of the power.
I think the gift by it's very nature is hard to detect or analyze. I vagely remember that there is no way to detect the gift with spells.
There is of course the disturbing effect it has on other people, but I finding an apprentice has to be a little challenge, and at some point one hasto take a chance.
I wrote a spell for my column in Hermes' Portal that can detect the Gift. Can't give full details because of my publishing agreement but I think I can say I called it a Base 5.
This is not official of course.